Through advancements in wireless access technologies, Internet Protocol (IP) based communications for multimedia applications became available for various types of mobile devices. Examples of such applications include white board discussions, video conferencing, Push to talk over Cellular (PoC), Voice over IP, real-time content sharing including videos/audio files, instant messaging, interactive gaming, and the like. One of the challenges to provide those IP multimedia application services is to provide a good user experience with these rich media applications among a large variety of different computing and mobile devices running over diverse (e.g., different types of wireless, fixed, or the like) networks.
An architectural framework for delivering internet protocol (IP) multimedia to mobile users over various types of wireless and fixed networks to provide the same level of standardization is called the IP Multimedia Subsystem (IMS). Many implementations of IMS employ Session Initiation Protocol (SIP) for session management, including, for example, to establish, modify, and terminate media sessions for various applications. Typically, several different roles of servers or proxies, collectively called Call Session Control Function (CSCF), are used to process SIP signaling packets in the IMS.
Among those servers, an I-CSCF (Interrogating-CSCF) is a server located at the edge of a particular domain. Its IP address is published in the Domain Name System (DNS) of the domain so that remote servers can discover an I-CSCF for a subscriber user, and use the discovered I-CSCF as a forwarding point (e.g., registering) for communication packets to the domain. For example, when a User Equipment (UE) initiates a registration process to the IMS, one I-CSCF is discovered for the UE and the I-CSCF assigns a proper Serving-CSCF (S-CSCF) for delivering IP multimedia services to the UE.
Currently, no consideration is given to the distance between the locations of a UE and its respective I-CSCF during the discovery process. Thus, in some cases, an I-CSCF that is located far from an UE is discovered for the UE even though another I-CSCF that is located closer to the UE is also available. Data packets traveling a long distance can become a major hindrance for providing a good user experience with rich or real-time media applications, especially among a large variety of different computing and mobile devices running over diverse networks.